Naltrexone has been shown to be of significant benefit in increasing abstinence and decreasing relapse in conjuction with various psychotherapies in alcohol dependent subjects over a 12 week period. There is however a significant number of alcohol dependent subjects that do not respond to natrexone. The serotonin system has been implicated in the pathogenesis of alcoholism and various serotonergic compounds have has tried with modest success in its treatment. The aim of this double blind placebo controlled outpatient trial is to improve the abstinence and relapse rates in alcohol dependent subjects on naltrexone through the addition of sertraline, a serotonin reuptake inhibitor. We propose to recruit 124 non-depressed alcohol dependent subjects from the Substance Abuse Treatment Unit (SATU) at Yale ask them to take naltrexone for one week and then randomize them into two groups. The first group will take naltrexone 50 mg daily plus placebo for 12 weeks, and the other will take naltrexone 50 mg plus sertraline 50 mg daily, increasing to sertraline 100 mg daily after one week, and ontinue at this does, if tolerated, for a further 11 weeks. All subjects will receive weekly relapse prevention group psychotherapy at SATU. Subjects will be monitored weekly for breath alcohol and drug screens, and also for compliance psychopathology and side effects. At the end of the 13 week trial subjects will be sent for appropriate follow up treatment if required. Subjects will be followed up at 6 and 12 months. The investigators hypothesize an increase in abstinence and a decrease in relapse in the alcohol dependent subjects through a synergistic effect of the opiate antagonist and the serotonin reuptake inhibitor.